MotoGP France: Smith suspects rising tyre pressure causes falls

Bradley Smith was one of eight riders to fall during Sunday's French MotoGP at Le Mans, all due to losing the front.

Asked if he had a theory to explain why many riders are still being caught out by the front tyre from new-for-2016 supplier Michelin, the Monster Yamaha Tech 3 rider gave a typically intelligent and insightful answer.

"If I knew, I'd maybe be paid more money to be a technical tyre director than a bike rider!" Smith began. "But my theory is that, when we are riding, it's usually the hottest part of the weekend, which is where we seem to be struggling most [with the front tyre].

"And then the constant demand of a race intensity, plus full fuel loads, is ramping up the front tyre temperature [and therefore pressure] quite a lot, I think. When the internal tyre pressure [sensors] come in, maybe it's something we can adjust."

Following Loris Baz's Sepang testing accident, tyre pressure sensors were made mandatory from the forthcoming Mugello round. The data gathered will therefore show if the tyre pressure is indeed increasing beyond the optimum working window, reducing grip.

If that does prove to be the case: "Maybe we can start with a little bit lower [pressure], so if it does ramp up it stays within the working range.

"I think potentially at the moment we're going over the working pressure, because of the intensity of the racing, all of us being hard on the brakes every corner - you're not quite as smooth as you usually are.

"The tyre [then] stops flexing and becomes a lot more rigid. I think that's the main issue. But because I don't have all that data to look at the moment, it's only a theory."

Smith's idea could explain why most falls seem to occur after the opening laps, rather than the early 'cold tyre' accidents sometimes seen on the previous Bridgestone rubber.

"It builds up, that's my gut instinct," Smith confirmed. "Potentially, we're going past the working tyre pressure of the Michelins, and it's not something that you can adjust accordingly. It's something we need to look at as a whole, every team and every rider, see if that's the case and adjust the regulations accordingly going into a race situation.

"From Mugello [with the compulsory tyre pressure sensors], we'll be able to analyse a little bit more. But I think it's one thing that Michelin need to keep an eye on, because it seems to be either later on in the race, or just when we start to drop off the lap times [that most accidents occur].

"So it's kind of, building, building, building, and then it just starts to taper off. And when the rear grip starts to go, it stops pushing on the front. If the front is a little bit stiffer than it usually is [due to the increase in pressure], away you go.

"That's my theory anyway, but like I said, I don't know until we actually see hard data. It's only speculation."

The description of the front tyre getting 'stiffer' would also fit with comments that riders have been caught out more by bumps this year.

"It didn't look like the riders that I saw fall today did much wrong," said Aspar Ducati's Eugene Laverty. "They weren't losing it with their knee down, they were losing it trail-braking before you would get a chance to catch it.

"There are a few bumps on this track in those places, and with the tyre last year we weren't affected by those bumps as much. It's as if the track got bumpier, but I know it didn't really. I think with the Michelins we can definitely feel the bumps that bit more, you can see the bikes moving into Turn 1.

"So it's a different characteristic and the tyres are working quite differently here because of the bumps. But the lap time is still good - and the pole time was faster than ever."

While Laverty crossed the line in eleventh, Smith made an early exit on lap 19 of 28, while holding seventh place.

"It's a shame more than anything else. Obviously disappointed for myself, but more so for the team," said Smith, competing in front of Tech 3's home fans for the final time before joining KTM in 2017. "First time all season we've looked positive, looked like we were on for a solid result.

"I wasn't 100% sure about the setting going into a race, because I've not raced it. I was trying to adapt as best as I could, seeing that I got a second wind towards the end, and I decided that pushing on to see if I could get somewhat closer to Pol and overtake Aleix was the right decision, and I just got caught out in Turn 5 like everyone else.

"I was slightly more inside than on previous laps, trying to carry my corner speed and just rolled off the side of the tyre. Just one of those things. It looks like the patch there was a little bit slippier than in other places. Looks like the repair work there was a little bit slippy, and that was it.

"Frustrating from my point of view, to end what's been a good weekend that way. All things considered, I was in seventh position, closing in on a factory Suzuki, not far from my team-mate whose been knocking on the top five door all weekend.

"I'll take it and we'll make the bike a little bit better for Mugello and hopefully keep it going there."